Many different devices have been proposed for clearing clogged fuel lines and plumbing lines. For example, Carroll U.S. Pat. No. 1,556,417 employs a manual air pump to backflush an automobile fuel line and to blast compressed air forward through the carburetor. Conn U.S. Pat. No. 3,426,774 and. Nakane U.S. Pat. No. 3,879,771 both employ CO.sub.2 cartridges that provide compressed gases to function as hydraulic rams, clearing blocked pipes or drains. Conn steps down the 750 psi cartridge pressure to between 60 and 100 psi in an accumulator cylinder 10 and then suddenly delivers that pressure to the clogged line. Bracken U.S. Pat. No. 2,147,593 applies physical hammer blows on a ram piston to deliver hydraulic blows to the clogged line. Engle U.S. Pat. No. 4,919,154 describes a combined pipe purging device which can deliver repeated physical shocks or repeated hydraulic shocks, and. can pump fluid into or out of the clogged system, or pump in chemical drain cleaners. Sundholm U.S. Pat. No. 5,007,444 combines liquid and gas for purging a clogged fuel line utilizing many short slugs of oil alternating with short bubbles of compressed air or nitrogen, all of which are first compressed and then suddenly decompressed, assertedly creating a forceful flushing pulse through the pipe system.
These prior patents indicate that different modes of delivering force to a conduit clog may be preferred in different circumstances. Compressed gas or the application of vacuum or a hydraulic shock, applying sudden pressure to fluid in the clogged conduit, have all been used in various situations, but these alternative pressure sources are not normally provided by the same equipment.